From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mathieu Desnoyers Subject: [RFC PATCH for 4.15 05/10] x86: Introduce sync_core_before_usermode Date: Fri, 10 Nov 2017 16:37:12 -0500 Message-ID: <20171110213717.12457-6-mathieu.desnoyers@efficios.com> References: <20171110213717.12457-1-mathieu.desnoyers@efficios.com> Return-path: In-Reply-To: <20171110213717.12457-1-mathieu.desnoyers-vg+e7yoeK/dWk0Htik3J/w@public.gmane.org> Sender: linux-api-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Boqun Feng , Peter Zijlstra , "Paul E . McKenney" Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, Andy Lutomirski , Andrew Hunter , Maged Michael , Avi Kivity , Benjamin Herrenschmidt , Paul Mackerras , Michael Ellerman , Dave Watson , Thomas Gleixner , Ingo Molnar , "H . Peter Anvin" , Andrea Parri , Russell King , Greg Hackmann , Will Deacon , David Sehr , Linus Torvalds , x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org, Mathieu Desnoyers List-Id: linux-api@vger.kernel.org Introduce an architecture function that ensures the current CPU issues a core serializing instruction before returning to usermode. This is needed to fix an existing core serialization bug on thread migration, and also needed by the membarrier "sync_core" command. Architectures defining the sync_core_before_usermode() static inline need to define ARCH_HAS_SYNC_CORE_BEFORE_USERMODE. Signed-off-by: Mathieu Desnoyers CC: Peter Zijlstra CC: Andy Lutomirski CC: Paul E. McKenney CC: Boqun Feng CC: Andrew Hunter CC: Maged Michael CC: Avi Kivity CC: Benjamin Herrenschmidt CC: Paul Mackerras CC: Michael Ellerman CC: Dave Watson CC: Thomas Gleixner CC: Ingo Molnar CC: "H. Peter Anvin" CC: Andrea Parri CC: Russell King CC: Greg Hackmann CC: Will Deacon CC: David Sehr CC: Linus Torvalds CC: x86-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org CC: linux-arch-u79uwXL29TY76Z2rM5mHXA@public.gmane.org --- arch/x86/Kconfig | 1 + arch/x86/include/asm/processor.h | 10 ++++++++++ include/linux/processor.h | 6 ++++++ 3 files changed, 17 insertions(+) diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig index 01f78c1d40b5..54fbb8960d94 100644 --- a/arch/x86/Kconfig +++ b/arch/x86/Kconfig @@ -62,6 +62,7 @@ config X86 select ARCH_HAS_SG_CHAIN select ARCH_HAS_STRICT_KERNEL_RWX select ARCH_HAS_STRICT_MODULE_RWX + select ARCH_HAS_SYNC_CORE_BEFORE_USERMODE select ARCH_HAS_UBSAN_SANITIZE_ALL select ARCH_HAS_ZONE_DEVICE if X86_64 select ARCH_HAVE_NMI_SAFE_CMPXCHG diff --git a/arch/x86/include/asm/processor.h b/arch/x86/include/asm/processor.h index bdac19ab2488..6ce996a7c730 100644 --- a/arch/x86/include/asm/processor.h +++ b/arch/x86/include/asm/processor.h @@ -706,6 +706,16 @@ static inline void sync_core(void) #endif } +/* + * Ensure that a core serializing instruction is issued before returning + * to user-mode. x86 implements return to user-space through sysexit and + * sysretq, which are not core serializing. + */ +static inline void sync_core_before_usermode(void) +{ + sync_core(); +} + extern void select_idle_routine(const struct cpuinfo_x86 *c); extern void amd_e400_c1e_apic_setup(void); diff --git a/include/linux/processor.h b/include/linux/processor.h index dbc952eec869..7d12e6fa050e 100644 --- a/include/linux/processor.h +++ b/include/linux/processor.h @@ -68,4 +68,10 @@ do { \ #endif +#ifndef ARCH_HAS_SYNC_CORE_BEFORE_USERMODE +static inline sync_core_before_usermode(void) +{ +} +#endif + #endif /* _LINUX_PROCESSOR_H */ -- 2.11.0